Conventionally, an air-conditioning system that diagnoses an operation state of the air-conditioning system using an operation-state diagnosing table based on information on the operation state of the air-conditioning system collected by a remote controller, and that displays a diagnosing result on a display screen has been put into practical use to enable a maintenance-inspection person, that is, a service person to easily check the operation state of the air-conditioning system in inspection of the air-conditioning system.
Patent Literature 1, which is an example of a technique that compares a preset threshold value and a current state amount to perform a fault diagnosis, describes a problem that “a conventional fault diagnosis method for a refrigeration device grasps a state of the refrigeration device by comparing a threshold value set by accumulation of past data or a preset threshold value with the current state amount and, in order to perform a fault diagnosis in a refrigeration device with a compressor having a controllable performance mounted therein, it is necessary to change the threshold value every time a refrigeration performance changes or to preset the threshold value for each of refrigeration performances”. Patent Literature 1 discloses a refrigeration device that “enables a fault diagnosis with high accuracy to be easily performed even in a case where the refrigerating performance is changed, by predicting normal input values of the refrigeration device and a compressor only from a current measurement value of the refrigeration device and comparing the predicted normal input values with actual measurement values of the input values”.